What is an AI companion? How they work, and the main types

How lawmakers define an AI companion

AI companions are now common enough to have legal definitions, and they agree on the core idea:

• New York (General Business Law Article 47, in force since 5 November 2025): systems "designed to simulate human relationships with users", such as an AI friend or romantic partner, which may remember personal details, adapt to user preferences and are designed to keep users engaged.
• California (SB 243, 2025): an AI system with a natural language interface that gives "adaptive, human-like responses" and is "capable of meeting a user's social needs".
• The FTC (2025 inquiry): chatbots that "mimic human characteristics, emotions, and intentions" and are designed to communicate like a friend or confidant.
• China (December 2025 draft): "anthropomorphic interactive services" that simulate human personality traits, thinking patterns and communication styles and engage in emotional interaction.

The common thread: a relationship that continues over time, with memory and emotional language, rather than one-off answers.

How AI companions work

Under the surface, an AI companion is a large language model given a fixed character to play. Each time you send a message, the app hands the model the character description, any facts it has saved about you and the recent conversation, and the model writes the next reply in character.

Three extras turn that into a companion:

• Memory that stores facts about you and brings them back later.
• Media: pictures, voice notes and sometimes live calls, made by separate image and voice models.
• Initiative: check-ins and notifications that make the relationship feel two-sided.

Our guide to what an AI girlfriend is explains each part in more detail.

The main types of AI companion

1. Friend and well-being companions. Built as a supportive friend, usually without explicit content. Replika is the best-known and claims 42,160,934 users worldwide on its homepage.
2. Romantic companions (AI girlfriends and boyfriends). Built as a partner, with flirting, pictures and usually 18+ chat. We track 31 of these apps, and 29 allow explicit content.
3. Character chat platforms. Huge libraries of user-made characters, from anime heroes to study buddies. Character.AI has 20 million monthly active users, according to TechCrunch.
4. General assistants used as companions. Many people form bonds with tools like ChatGPT that were never designed for it. MIT researchers found members of an AI relationships community on Reddit more often used general-purpose models than dedicated companion apps.

Not everything called an "AI companion" is one. Zoom's AI Companion, for example, is a meeting assistant that summarizes calls; it is not built for a personal relationship.

What people use AI companions for

• Company and support. In a study of 1,006 student Replika users, people described the app as a friend, a therapist and an "intellectual mirror", and 90% reported loneliness.
• Personal advice. According to the Harvard Gazette, 27% of American adults use chatbots for personal matters such as relationship advice and social connection.
• Romance. 16% of US singles had engaged with AI as a romantic companion in Match's 2025 study.
• Social practice and roleplay. About one in three US teens who use AI companions use them for social interaction, including roleplay and conversation practice, according to Common Sense Media.

Benefits and risks

The research points both ways. A 15-minute chat with an AI companion eased loneliness about as much as talking with a person in Harvard Business School studies, though the effect did not build up over a week. A four-week MIT Media Lab study found heavy voluntary use went with more loneliness and emotional dependence.

The practical risks are privacy, spending and design that keeps you hooked. Companion apps met 37% of goodbyes with emotional manipulation in a Harvard Business School working paper, and Mozilla found most romantic chatbots may share or sell personal data. Our guide to whether AI girlfriends are bad for you covers the evidence in full.

What AI companions cost

Most are free to start and charge a subscription for full use. Replika costs $4.17 a month on its cheapest plan or $14.99 month to month, with this free plan: Free chat, romance and calls are paid. Nomi AI costs $8.33 a month on its cheapest plan. Across the 31 romantic companion apps we track, the median cheapest plan is $7.75 a month and the median month-to-month price is $14.99.

Pictures, voice calls and extra characters often cost tokens or credits on top. Our AI girlfriend cost guide compares every published price, and our comparison of an AI companion vs an AI girlfriend helps you pick the right type.